CEL comes and goes, P1123 & P1125 Lean Limit. Is Airflow Sensor

[Wonko The Sane]

Hey Gents,

I have a check engine light that seems to come on about half the time. It will pop on and stay on for a few days until it decides that it's had enough and then disappears for a few days.

According to Durametric, the error codes are P1123 and P1125 which is Oxygen Sensing Adaptation Area 1 (Cylinders 1 - 3) - Lean Threshold and Cylinders 4-6, respectively.

After reading through a few other posts with an external link to Mass Airflow Sensor cleaning instructions, it appears that my two main troubleshooting efforts should focus on either a vacuum leak around the intake plenum area or replacing the MAS.

My thoughts on it are that if it were a vacuum leak, it wouldn't go away on its own merits. Although modern cars are amazing, they don't generally mend physical failures such as cracks in the plastics and rubbers.

This singles out the MAS, but can anyone think of anything else to check before blindly go replacing it? I want to take care of this problem now before the new owner takes delivery of it.

Thanks!

[edevlin]

It could actually be a number of things, MAF sensor, vacuum leak, low efficiency cat or oxygen sensor, problems with wiring to sensors or more. I dont like those stinken CEL lights....

Ed

[Wonko The Sane]

Good list, Ed.. see if my thinking is logical for each one:

MAF sensor - This is what I'm leaning towards, I think it makes the most sense by process of elimination.
vacuum leak - Would this be intermittent?
low efficiency cat - The code says "range 1", which I'm assuming is talking about the oxygen sensors before the cats, so I wouldn't think that would affect it..
low efficiency oxygen sensor - Shouldn't be. All 4 sensors are less than 7k old, and this CEL shows up for both banks, it would only come up with cylinders 1-3 or 4-6 if it were one failing sensor, not both sides I would think
problems with wiring to sensors - Again, I think it would only throw a code for one side, not both.

I dont like those stinken CEL lights - I hate these buggers, too! I think everyone does

[edevlin]

I would also suspect the MAF because of the intermitent nature of the CEL.

Ed

[NickCats]

Wonko,

I would suggest cleaning the MAF. Worked for me :

My First CEL

Dude, I cleaned my MAF !

Nick

[Wonko The Sane]

Thanks for the suggestion, NickCat! I did already clean it once, and it's still doing it, so I'm thinking new MAF time...